Preheat oven to 400°F (200°C). Scrub potatoes, pat dry, and pierce several times with a fork. Rub all over with olive oil and salt. Bake directly on the oven rack for 60-75 minutes until tender.

While potatoes bake, melt butter in a large skillet over medium heat. Add garlic and cook until fragrant (about 30 seconds). Add chopped shrimp and cook for 2-3 minutes until pink. Remove shrimp and set aside.

In the same skillet, lower heat and whisk in the softened cream cheese, heavy cream, and Cajun seasoning until smooth. Stir in 1 cup of the shredded cheddar cheese until melted.

Remove skillet from heat. Gently fold in the cooked shrimp, lump crab meat, and sliced green onions. Season with salt and pepper to taste.

Once potatoes are cool enough to handle, slice them in half lengthwise. Scoop out the flesh, leaving a 1/4-inch border. Add the scooped potato flesh to the skillet with the seafood mixture and mash to combine.

Spoon the filling back into the potato shells. Top with the remaining 1/2 cup of cheddar cheese. Place on a baking sheet and bake for 15-20 minutes, or until the filling is hot and the cheese is bubbly and golden.

Garnish with extra green onions and serve immediately.